That means that .8bf files are not associated with Photoshop on our system, but that isn't really important. As long as you have the plugins in the Plug-Ins sub folder of the Photoshop folder they should appear in Photoshop.

Please notice that there are different types of plugins. Maybe you didn't download filter plugins, but e.g. automation plugins. These different plugin types appear in different menu places in Photoshop.